1. Field of the Invention
This invention relates to an air jet for the production of entangled multifilament yarn.
2. Prior Art
It is known to entangle multifilament yarns by means of an air jet apparatus in which air is introduced into a chamber at an angle to the travel of yarn to form a plural vortex turbulent air zone that entangles or interlaces filaments of the yarn. One such apparatus is disclosed in my U.S. Pat. No. 3,983,609, issued Oct. 5, 1976, which relates to an air entangling apparatus wherein the air jet is in the form of a block and in which an air stream enters a central bore at substantially right angles thereto. The bore extends all the way through the block and preferably has a uniform cross section so that air leaves at both ends of the bore. The incoming air jet strikes the upper wall of the central bore at a point opposite to the point of air introduction and splits to form two vortices in the upper portion of the central bore. Yarn introduction into the central bore is upstream from the air jet and is at an angle so that the yarn moves to the top of the turbulent air stream in the area of formation of the air vortices, where it oscillates back and forth across the stream. The yarn moves for a short distance countercurrent to the air leaving the upstream end of the central bore and then cocurrent with the air stream leaving the other end of the bore. The angled introduction of the yarn and the countercurrent air flow urge the yarn toward the top of the bore and hold the yarn in the upper portion of the bore in the area of formation of the air vortices.
When the apparatus of U.S. Pat. No. 3,983,609 is used to combine two or more multifilament yarns a product is obtained which is useful for many purposes. However, there are some end uses which require combined yarns having a tighter, more compact filament entanglement. In particular, problems have been encountered with some looms, such as Sulzer looms, which form a shed by separating the warp yarns with a series of very closely spaced fingers that catch on any loops protruding from the surface of the yarn.